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The frequency of malocclusions in adults isequal to or greater than that observed in chil-dren and adolescents.1 Crowding and spacing areamong the most common problems in adults,with crowding affecting about 24% of women

and 14% of men, and spacing found in 8% ofwomen and 13% of men.1

Despite their need for orthodontic treat-ment, however, adults are often averse to wear-ing traditional fixed appliances with wires,bands, and brackets. The Invisalign System*now makes it possible for orthodontists to offeradult patients requiring full-mouth orthodontictreatment an esthetically agreeable solution,using a computer-assisted technology that pro-duces a series of clear plastic overlays.

Clear plastic overlay appliances take a vari-

ety of forms, including retainers,2-4

night guards,TMJ splints, and bleaching trays. Although suchappliances have sometimes been used for minortooth movement,2-5 this has traditionally requireda dental technician to manually reset the teeth ona plaster model and form an overlay appliance tofit each stage of treatment. Cases involving manytreatment stages have therefore required exten-

sive manual labor, which is both costly and vul-nerable to human error and inaccuracies.

Recent developments in technology havenow made it possible, with the Invisalign Sys-tem, to take a single impression of a patients

dentition, and use that to:1. Create a final setup.2. Project stages of tooth movement from theinitial state to the final state.3. Create a series of clear, custom-made appli-ances, called aligners, that move the teethaccording to the projected stages of movement.

We initiated a feasibility study of the Invis-align appliance at the University of the Pacificmore than two years ago. Initially, we started 10patients with relatively uncomplicated malocclu-sions involving mild-to-moderate crowding and

space closure, as shown in this report. Based onour success with those initial cases, we thenstarted treatment on 30 additional patients withmore complex orthodontic problems, includingdental expansion, Class II and Class III correc-tion, and various types of extraction treatment.These cases are now nearing completion and willbe reviewed in a later publication.

Align Technology also selected about 25private orthodontic practices to serve as addi-

VOLUME XXXIV NUMBER 4 2000 JCO, Inc. 203

The Invisalign System in AdultOrthodontics: Mild Crowding and

Space Closure CasesROBERT L. BOYD, DDS, MEDROSS J. MILLER, DDS, MSVICKI VLASKALIC, BDS, MSD

Dr. Boyd is a Diplomate of the American Board of Orthodonticsand Professor and Chairperson, Department of Orthodontics,School of Dentistry, University of the Pacific, San Francisco, CA94115. Drs. Miller and Vlaskalic are Assistant Clinical Profes-sors, Department of Orthodontics, School of Dentistry, Universi-ty of the Pacific. Dr. Miller is also the full-time Orthodontic Dir-ector of Align Technology, Inc., Sunnyvale, CA. Drs. Boyd andVlaskalic were compensated for their efforts in the conduct ofthis study (but do not own stock in the company).

Dr. Boyd Dr. Miller Dr. Vlaskalic

*Trademark of Align Technology, Inc., 442 Potrero Ave.,

Sunnyvale, CA 94086.


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tional initial-feasibility test sites for theInvisalign System. Because the technology isstill being developed, corporate policy has beento allow only qualified orthodontists to partici-pate in the use of the appliances.

Patient Selection and Records

A candidate for orthodontic treatment withthe Invisalign System should have fully eruptedpermanent teeth, with growth completed. Thereis no age requirement, but the ability to complywith the treatment regimen of nearly full-timewear is mandatory.

Once a patient is determined to be a goodcandidate for Invisalign treatment, the usualorthodontic records are taken, including studycasts, photographs, and radiographs. Polyvinyl-siloxane impression material** must be used,because it yields highly accurate impressions that

remain stable for as long as three weeks andallow multiple pours.

Fabrication of Aligners

The impressions and wax bite are sent toAlign Technology with a detailed treatment-

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The Invisalign System in Adult Orthodontics

Fig. 1 Case 1. 23-year-old female with multiple upper and lower diastemas before treatment.

Fig. 2 Case 1. Align Technology computer-gener-

ated image of malocclusion.

**ESPE America, Box 111, Norristown, PA 19404.


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planning form. Align Technology produces athree-dimensional computer image from theimpressions and performs a virtual treatmentusing a proprietary software program. A graphicversion of the treatment is then made availablefor the treating orthodontist to download fromthe Internet and view on a personal computer. Ifnecessary, the clinician provides feedback on theproposed final position and intermediate toothmovements to Align Technology, and adjust-ments are made until the orthodontist is satisfiedwith the treatment plan and prospective results.

Once treatment is approved, Align Tech-nology fabricates a set of clear plastic aligners,each about .030" thick. Each pair of upper andlower aligners in the series (single-arch treatmentis also an option) incorporates a small adjust-ment, allowing for .25-.33mm of movement. Thenumber of aligners per patient depends on thenumber of stages required to complete the treat-ment.

The aligners are sent to the orthodontist,

who delivers them to the patient with instructionsfor use. The overlays should be worn 20-22hours per day and removed only for eating,drinking, and toothbrushing or flossing. Thepatient wears each pair of aligners for one to twoweeks before moving on to the next pair in theseries. These appliances are disposable and virtu-ally undetectable from about two feet away.

Case Reports

Four completed cases are presented here,two requiring space closure and two involvingmild crowding. The photographs were madefrom original prints taken by a commercialorthodontic laboratory (Cases 1 and 2) or copieddirectly from 35mm slides (Cases 3 and 4). Theywere not digitally altered in any way.

Case 1

A 23-year-old female presented with the

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Boyd, Miller, and Vlaskalic

Fig. 3 Case 1. Patient after treatment.


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chief concern of spacing between the teeth. Shewas diagnosed with multiple upper and lowerdiastemas (Fig. 1). Starting with impressions ofher teeth, Align Technology used the InvisalignSystem to create a computerized three-dimen-sional image of her teeth (Fig. 2) and then, fol-lowing the treatment plan, to generate a series ofimages that showed the spaces closing from theinitial, untreated state to the final, treated state.Align then produced a series of aligners to matchthe desired stages of tooth movement (Fig. 3).

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Fig. 4 Case 2. 33-year-old male with multiple upper and lower diastemas before treatment.

Fig. 5 Case 2. Align Technology computer-gener-ated image of malocclusion.



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Case 2

A 33-year-old male was diagnosed withmultiple upper and lower diastemas (Fig. 4).Treatment was aimed at closing the spacesbetween the teeth, using aligners (Fig. 5). Afternine months, space closure was achieved suc-cessfully, despite some root tipping that occurredaround the mandibular central incisors (Fig. 6).

Case 3

A 35-year-old male displayed maxillarycrowding (Fig. 7). This was a case of relapseafter orthodontic treatment involving four bicus-pid and mandibular incisor extractions. Thetreatment plan was designed to flare the maxil-lary incisors using the Invisalign System (Fig. 8).Five months of treatment produced a satisfactory

result (Fig. 9).

Fig. 6 Case 2. Patient after nine months of treatment.




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Fig. 7 Case 3. 35-year-old male with maxillarycrowding before treatment.

Fig. 8 Case 3. Align Technology computer-gener-ated image of malocclusion.


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Fig. 9 Case 3. Patient after five months of treatment.


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Fig. 10 Case 4. 38-year-old female with crowding in both arches before treatment.

Fig. 11 Case 4. Align Technology computer-generated images of malocclusion.

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Case 4

A 38-year-old female presented withcrowding in both arches (Fig. 10). The treatmentplan involved reproximation and minor toothmovement. Impressions were used to generate

the computerized three-dimensional models ofboth arches (Fig. 11). After eight months of treat-ment with the Invisalign System, the maxillarylateral incisors could perhaps have been rotatedslightly more, but the overall crowding was alle-viated (Fig. 12).

Fig. 12 Case 4. Patient after eight months of treatment.




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Discussion

In 1945, Kesling published the first articleon the use of elastic positioners to move teeththat had been realigned in a wax setup.6 He real-ized that the lab requirements would be signifi-cant, and did not envision this as a practicalmeans of more extensive treatment. He did havethe foresight, however, to state that the technolo-gy would some day be available to make suchtreatment possible.6 The technology described inthis article fulfills Keslings vision.

The Invisalign System also addresses theneeds of many adult patients by providing analternative to fixed appliances in appropriatecases. Aligners offer several advantages overconventional fixed appliances: First, they areclear, and therefore more esthetically acceptable,particularly for adults. Also, aligners are general-ly more comfortable to wear, and they areremovable, allowing better oral hygiene.3,4,7

Because a high degree of compliance isneeded for this system to be effective, theInvisalign System is currently recommendedonly for adults. Adolescents with fully erupted

permanent teeth (except third molars) may alsobe candidates for this approach, as long as theyhave been screened for compliance.

The Invisalign System has several potentialdisadvantages. Some patients may not wear thealigners enough for treatment to be effective.Being removable and clear, they may also be

lost, although a study of 40 patients, comparingclear Essix*** retainers to conventional Hawleyretainers, did not find a statistical difference inthe numbers of people losing either type of appli-ance.7 Due to occlusal coverage, slight (1/4-1/2mm) posterior tooth intrusion may occur. Thisis generally dealt with in the retention period,which allows for settling when these teeth arefree to erupt into occlusal contact.

Conclusion

The Invisalign System has opened up a newarea of adult orthodontics, serving patients whomay not want conventional fixed appliances orfor whom traditional removable appliances maybe unsuccessful.

ACKNOWLEDGMENTS: The assistance of Sharon Welner, PhD,of BioMedCom Consultants, Inc., Montreal, Canada, in writing themanuscript is gratefully acknowledged.

REFERENCES

1. Buttke, T.M. and Proffit, W.R.: Referring adult patients fororthodontic treatment, J. Am. Dent. Assoc. 130:73-79, 1999.

2. Ponitz, R.J.: Invisible retainers, Am. J. Orthod. 59:266-272,1971.

3. McNamara, J.A.; Kramer, K.L.; and Juenker, J.P.: Invisibleretainers, J. Clin. Orthod. 19:570-578, 1985.

4. Sheridan, J.J.; Ledoux, W.; and McMinn, R.: Essix retainers:Fabrication and supervision for permanent retention, J. Clin.Orthod. 27:37-45, 1993.

5. Rinchuse, D.J. and Rinchuse, D.J.: Active tooth movement withEssix-based appliances, J. Clin. Orthod. 31:109-112, 1997.

6. Kesling, H.D.: The philosophy of the Tooth PositioningAppliance, Am. J. Orthod. 31:297-304, 1945.

7. Lindauer, S.J. and Shoff, R.C.: Comparison of Essix andHawley retainers, J. Clin. Orthod. 32:95-97, 1998.

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***Registered trademark of Raintree Essix, Inc., 1069 S. JeffDavis Parkway, New Orleans, LA 70125.